First, we've got population. The world today has 6.8 billion people. That's headed up to about nine billion. Now, if we do a really great job on new vaccines, health care, reproductive health services, we could lower that by, perhaps, 10 or 15 percent.
https://www.ted.com/talks/bill_gates_innovating_to_zero/transcript?language=en
I find it funny that people always say stuff like "these people tell you exactly what they want to do and no one listens!". Then when you get the quote of them "telling you what they're going to do" it's some nonsense like this that fits in nicely with their other beliefs and things they've said and doesn't fit into some "massive depopulation event".
Bill Gates is evil and the whole appearance he puts on is total garbage sprinkled in with the Science™ bullshit so it's likely he's just putting all this together to make sense to normies and hide his evil intentions underneath but this quote absolutely does not "prove" Bill Gates wants massive depopulation (which he probably does) and is not a case of Bill Gates "saying what he's going to do and no one listening".